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Avalanche Forecast

Archived

Nov 25th, 2021–Nov 26th, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

New snow and strong southwesterly winds have created fresh storm slabs reactive to human triggers. These slabs will be especially reactive on lee features at treeline and above.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

THURSDAY NIGHT: Mostly cloudy with flurries; 5-10 cm / Strong, southwesterly winds / Low of -6 / Freezing level 400 m.

FRIDAY: Mostly cloudy with isolated flurries; 3-5 cm. / Strong, southwesterly winds / High of -3 / Freezing level 500 m.

SATURDAY: Snow; 10-15 cm / Strong, southerly winds / High of -1 / Freezing level 700 m.

SUNDAY: Snow; 15-20 cm / Strong, southwesterly winds / High of -1 / Freezing level 1000 m.

Avalanche Summary

Large natural avalanches up to size 3 were reported on west and northwest aspects in the alpine on Wednesday. 

These recently formed storm slabs are expected to remain reactive to human triggers, especially on lee features at treeline and above.

Snowpack Summary

30-40 cm of recent snow and strong southerly winds have created fresh storm slabs reactive to human triggers at treeline and above.

A progression of intense storms over the past month has resulted in impressive snow depths, with total depths at treeline ranging from 200 to 250 cm. The snow from these storms has generally been strengthening and bonding quickly. A prominent crust from early November can be found in the lower snowpack, but does not appear to be a problem. Many areas below treeline are still below threshold depths for avalanches.

Terrain and Travel

  • Give the new snow time to settle and stabilize before pushing into bigger terrain.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded terrain features.
  • Remember that the snowpack will be significantly different at higher elevations than lower down.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.